Fashion’s muse of the moment, the 18-year-old model Ruslana Korshunova, from Kazakhstan, is known in the industry as “the girl with the long hair”, because until she was signed up by Models 1, her now bottom-length locks came down to her knees. In Kazakhstan, long hair is a sign of beauty, and hers had never been cut. Now it has, and Korshunova has been swamped with offers of work from top designers, magazines and photographers. At Kenzo’s autumn/winter show, her hair perfectly captured the Victorian voyager mood. Using Tigi Bed Head’s Cocky Paste (£12; 020 8338 1300), the session stylist Eugene Souleiman went for the traveller vibe, gathering hair into loose buns to give it texture, and taking it down just before they went on stage. “We wanted something a bit crusty, so the girls looked as if they’d been backpacking through India, but still had beautiful hair,” says Souleiman.

Even with the traveller look, however, the modern take on long hair is all about condition. “The most important thing with long hair is to treat it gently,” says the trichologist Philip Kingsley, whose clinic at Urban Retreat in Harrods offers specific treatments for long hair. “On average, long hair is three years old,” he explains, “which means the ends have had up to three years of environmental and styling damage, so it’s a good idea to use a leave-in conditioner on the tips.” His PM36 protective moisturiser (£18; 020 7629 4004) is a lightweight product that can be left in. “I also prefer combs over brushes,” he says. “Women with long hair tend to drag a brush through their hair, which pulls and breaks it. With a comb, you have to be more careful.”

For those trying to grow their hair, Kingsley has one piece of advice: “Don’t cut it.” This will be manna from heaven for fans of long hair who often battle with salon stylists intent on hacking off inches. Generally, hair salons today focus on cutting and colouring (not surprisingly, the most lucrative for them), so traditional hairdressing skills have fallen by the wayside. “Most salon stylists like to leave their mark, which can have a bit to do with ego, ” says Gray, “and that’s easier to accomplish with a cut. Long hair can go three or four months without a cut,” he says. “Especially when you consider that a hairdresser’s inch is more like three.”

The average Caucasian hair has a life span of four years and grows up to 24in; with Asian hair, the average is seven years and 42in. Hair grows on average half an inch a month, so someone who has an inch cut off every couple of months will see little change in the length. The make-up artist and designer Denise Kum, who has worked on films such as Finding Neverland, Last Samurai and Sylvia, is often called upon to tidy up actresses’ long hair, but for reasons of continuity, she has to do it without losing any of the length. “Long hair is nice when it has some layers, rather than that blunt-cut look,” she says.

To get rid of split ends without losing too much length, Kum suggests taking the hair in small sections and twisting it. “When you do this, only the split ends will stick out, which you can snip off with scissors,” she says. “It’s a great way of growing your hair long and keeping it in good condition.”

HEALTHY-HAIR GUIDE

BRUSHING Using a comb with wide teeth, start at the tips and work upwards towards the roots. Philip Kingsley’s combs have teeth that are saw-cut — these are better than the moulded comb, which can leave jagged edges that cut into the hair (from £4.50; 020 7629 4004).

SHAMPOO AND CONDITIONING Great shampoos and conditioners for long hair include PhytoNeutre Shampoo (£18), and Phyto7 Leave-in Conditioner (£11, both by Phyto; 020 7620 1771); Marlies Moller Liquid Hair foam (£17, from Harrods; 020 7730 1234); Philip Kingsley Moisture Balancing Shampoo and Conditioner (from £9.95, as before); and Aveda Damage Remedy Shampoo and Conditioner (from £15; 0870 034 2380).

HEAD MASSAGE Great for increasing circulation to the scalp and hair follicles. Kérastase Express Nourishing Ritual is an in-salon treatment that gives a conditioning boost with head-and-shoulder massage (£15; 0800 316 4400).

TREATMENTS Philip Kingsley Elasticizer (£20, as before) — use once a week for increased shine, smoothness and resilience; alternatively, Phyto PhytoCyane Treatment is designed to stimulate hair growth and strengthen the hair (£28, as before).

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